In the glass industry, a relatively large amount of thermal energy is consumed in the melting of the starting materials of the glass in the melting furnace. Unfortunately, the efficiency of the melting furnaces is relatively poor because the temperature of the residual gases from these furnaces is determined by the melting temperature of the glass or its starting materials. Accordingly, various attempts have been made to improve the overall efficiency of these melting installations.
In practice, therefore, recuperators for example are connected to the melting furnaces, these recuperators generally comprising two chambers which are lined with bricks accumulating the heat and, hence, stacked and which operate in an alternately periodic manner so that one of the chambers is traversed for a predetermined period of time by the residual gases from the furnaces (which thus heat the bricks) to be removed through the chimney, whilst cold fresh air simultaneously flows through the second chamber and is heated to act as combustion air for the melting furnace. Under these conditions, therefore, one of the recovery chambers is on each occasion heated in an alternately periodic manner by the residual gases from the furnace at the same time as these residual gases give off some of their thermal energy (to the bricks) and are slightly cooled, whilst cooling of the heated bricks and simultaneous reheating of the combustion air take place in the second chamber conjointly with the operations mentioned in the first place. Apart from the fact that a constant cyclic inversion of the chambers of the recuperator modifies the combustion temperature of the melting furnace, it has been found that efficiency cannot reach the required level.
In other known installations, the melting furnace is preceded by a vessel which is intended for preheating the starting materials and into which the residual gases emanating from the melting furnace are introduced and utilised to the maximum for preheating the starting materials. Unfortunately, it has been found that, in this case, too, the thermal efficiency is still inadequate because, in addition to this deficiency, there is a further disadvantage that these preheaters operate inadequately in the event of a different grain size distribution of the particles in the sense that the fine particles of dust are partly drawn off, and the starting materials leaving the preheater frequently have a composition entirely different from that which they have on entering the preheater. Accordingly, these known heating installations are relatively expensive with regard to the required efficiency level which is still relatively low.